The present invention relates in general to temperature control systems, and in particular to a temperature control system that integrates magnetic sensitive elements and infrared sensor on a single chip for a reliable and cost effective implementation.
There are a variety of consumer goods that require a temperature control mechanism. For these types of goods, a control knob typically adjusts the target temperature within a given range as determined by the application. In an electric iron, for example, the temperature of the sole plate is controlled and adjusted to a setting determined by the characteristics of the material to be ironed. The electric iron must therefore have the capability to detect the user""s requested temperature, measure and control the temperature produced by the iron.
To detect the position of a temperature control knob, existing devices typically use a potentiometer whose resistance value changes as the knob is rotated. Thus, by measuring the resistance value of the potentiometer, the device detects the setting of the control knob. While this implementation is relatively cost effective, it has the disadvantage of relying on a physical contact between the fixed resistance element and the wiping element. In an environment where the temperature is very high by the nature of the application, good reliability and accuracy is difficult to achieve at an acceptable cost. Another method for temperature control uses a bimetallic strip element in close proximity to the heated parts of the structure. Cost and reliability, however, remain difficult requirement to meet with this type of implementation as well. In the consumer market, the selling price of such products is of paramount importance, and therefore the cost of manufacturing becomes a significant factor.
There is therefore a need for a low cost and robust temperature sensing and control system that is suitable for the consumer market.
The present invention provides an integrated and cost-effective temperature sensor that can both detect the position of a control knob and measure the temperature of the controlled part. In a preferred embodiment, there is integrated onto a single piece of silicon a plurality of magnetic sensitive elements and an infrared sensor. Broadly, the magnetic sensitive elements determine the angular position of a magnetic field created by a magnet attached to the control knob. The magnet and its field rotate around the integrated circuit affecting the magnetic sensitive elements variously such that the position of the control knob can be determined. The infrared sensor in turn measures the radiation from the temperature controlled part such as to determine its temperature.
Accordingly, in one embodiment, the present invention provides an integrated circuit fabricated on a silicon substrate including a plurality of magnetic sensitive elements; position sensing circuit coupled to the plurality of magnetic sensitive elements, and configured to detect a relative position of an external magnet with respect to the plurality of magnetic sensitive elements; an infrared sensor; and a radiation sensing circuit coupled to the infrared sensor, and configured to detect an amount of radiation from an external heat source.
In another embodiment, the present invention provides a temperature control system including a temperature setting mechanism having a magnet attached thereto; and a silicon die disposed near the magnet, wherein integrated onto a first surface of the silicon die are a plurality of magnetic sensitive elements and an infrared sensor, and wherein the first surface of the silicon die faces toward a source of heat to be controlled and faces away from the magnet.
The nature and advantages of the temperature control system of the present invention will be better understood with reference to the detailed descriptions and drawings below.